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Chronic administration of the pineal hormone melatonin in a low dose (0.75 mg) improved memory and optimized individual time perception in a group of young volunteers. These changes were pronounced even two weeks after termination of the drug administration. The expression of the melatonin effect was depended on the chronotype of humans tested.
Adults with attention deficit hyperactivity disorder (ADHD; n = 104) were compared with a control group (n = 64) on time estimation and reproduction tasks. Results were unaffected by ADHD subtype or gender. The ADHD group provided larger time estimations than the control group, particularly at long intervals. This became nonsignificant after controlling for IQ. The ADHD group made shorter reproductions than did the control group (15- and 60-s intervals) and greater reproduction errors (12-, 45-, 60-s durations). These differences remained after controlling for IQ and comorbid oppositional defiant disorder, depression, and anxiety. Only the level of anxiety contributed to errors (at 12-s duration) beyond the level of ADHD. Results extended findings on time perception in ADHD children to adults and ruled out comorbidity as the basis of the errors.
Time estimation by the production method and pulse rate under resting but attentive conditions were investigated in 92 healthy males. Subjects estimated intervals of 30, 60, and 180 sec following which they participated in an hour-long watchkeeping task during which pulse rate was recorded. Both the time estimates and pulse rate in the group covered a wide range of values. Correlations between pulse rate and time estimates in the group were all negative; the largest and only statistically significant correlation was equal to -.205. It was concluded that pulse rate plays only a minor if not insignificant role in the perception of time.
Three experiments were conducted to assess the effects of the Stroop task (color-word incongruities) on observers' estimates of 30-sec. inspection periods. The experiments differed in psychophysical procedure; the three classic methods of production, reproduction, and verbal estimation were employed. Observers underestimated the passage of time, compared to doing nothing, when they were engaged on the Stroop task. However, judgments of duration on the Stroop task were shorter than those made in the control condition of naming color dots only when the method of production was employed. These findings are similar to results with mental arithmetic tasks and contribute to the understanding of the relationship between cognitive processing and time perception.
The paper analyses results after a study of visual fatigue by means of determining the perception time of a color successive contrast in children, aged from 10 to 13 years, before and after intensive dosed visual load. The revealed high percentage of visual fatigue in children (40.4-52.5%) is likely to be connected with the fact that the study was made in spring time when signs and body asthenization, avitaminosis are expressed. It was found that perception of a color successive contrast in children with eye myopization is shorter as compared with children with stably normal visual acuity.
Alterations in temporal estimation have been observed in Parkinson's disease (PD) and have been associated with dopaminergic dysfunction. To investigate whether deep brain stimulation might reverse these abnormalities in PD, patients treated with electrode implantation for subthalamic deep brain stimulation were required to reproduce time intervals in different experimental conditions (off deep brain stimulation/off therapy, on deep brain stimulation/off therapy, on therapy/off deep brain stimulation). Patients treated with deep brain stimulation in off deep brain stimulation/off therapy displayed the anomalous pattern of responses typically observed in PD. When subthalamic deep brain stimulation was turned on these abnormalities were significantly attenuated. Our findings reveal that subthalamic deep brain stimulation improves time perception in PD patients, supporting the critical role of basal ganglia in this cognitive function, probably mediated by facilitated thalamo-cortical projections to the prefrontal cortex.
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Relations between time perception and Type A behaviour were investigated. Extreme Type A (n = 26) and B (n = 28) male college undergraduates rated the appropriateness of 158 adjectives as descriptors of time. Adjectives were independently rated using seven-point Likert 'speed' and 'energy' scales. Analyses showed that Type As rate adjectives low in speed and energy as less descriptive of time than Type Bs and vice versa.
Performance on temporal discrimination of time intervals in the range of milliseconds is interpreted by the assumption of an internal clock; the higher the clock rate the better the temporal resolution of the internal clock will be, which is equivalent to more accuracy in timing of brief intervals. Although there is some evidence from animal and human studies suggesting that the clock rate depends on the effective level of brain dopamine (DA), the findings are not conclusive. Therefore, an alternative interpretation of the pharmacologic properties of the internal clock has been introduced. According to this interpretation, the internal timing mechanism can be seen as a biological rhythm that is susceptible to chronomutagenic agents, i.e., pharmacologic compounds that are able to produce an alteration in the period of a biological rhythm. To elucidate the pharmacologic properties of the internal timing mechanism, in a double-blind study either 1750 mg of the DA antagonist alpha-methyl-p-tyrosine (AMPT), 0.65 g/kg ethanol which possesses chronomutagenic effects, or placebo were applied to 80 male subjects. As measures of performance, difference threshold estimates in relation to a 50- and a 1,000-ms standard interval and respective response latencies were computed. Furthermore, urinary levels of DA, DOPAC, and HVA were quantified by HPLC analysis. Although AMPT treatment resulted in a pronounced reduction of more than 50% for DA, DOPAC, and HVA, temporal discrimination was not affected. On the other hand, ethanol induced a significant impairment in performance on temporal discrimination in the range of milliseconds as compared to placebo. Neither temporal discrimination in the range of seconds nor response latencies were affected by the drugs applied in this experiment. Our findings suggest that the internal timing mechanism underlying temporal discrimination of intervals in the range of milliseconds is independent of the effective level of brain DA. More likely, pharmacologically induced changes in clock rate appear to depend on the chronomutagenic effects of the drug applied. Furthermore, the absence of ethanol-induced changes in performance on temporal discrimination of longer intervals in the range of seconds supports the assumption of two distinct timing mechanisms underlying temporal discrimination in the millisecond and second range.
Human subjects were instructed to respond regularly at 3-second intervals while their brain waves were recorded and analyzed. When subjects were alert the time between two successive responses did not vary greatly; however, as subjects became increasingly drowsy these times lengthened and the mean voltage of the peak alpha frequency decreased.
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The role of attention in timing was evaluated in 2 experiments. In Experiment 1, participants reproduced the durations of melodies with either a coherent or an incoherent structure. Participants were tested under control (timing only) and detection (timing plus target detection) workload conditions. Reproductions were shorter and more inaccurate under detection conditions, and incoherent event structure extended the effect to a wider range of durations. In Experiment 2, participants reproduced the durations of auditory prose passages that represented 3 levels of mental workload and 3 levels of event structure. Both increases in workload and the degradation of structure led to inaccurate reproductions. The results point to the central role of attention in temporal experience.
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Stuttering is manifested as a disruption in speech timing, but it may stem from a more basic temporal disorder (R. D. Kent, 1984). We compared the ability of stuttering and nonstuttering adults to estimate protensity and to distinguish the relative lengths of short tones. We also examined whether there is a correlation between a person's degree of disfluency and the ability to measure protensity or judge the relative lengths of short tones. Twenty stuttering and 20 nonstuttering adults were given the Duration Pattern Sequence Test. They were also asked to estimate the lengths of 8 tones and silent intervals. A negative correlation was found between degree of disfluency and ability to determine the relative lengths of short tones. A positive correlation was found between degree of disfluency and length of protensity estimates.
The estimation of short-time intervals by 60 control subjects and 56 patients with affective disorders was investigated using the three different methods of metronome adjustment, verbal estimation, and operative estimation (production). The patients were diagnosed according to DSM-III criteria. A group with major depression with melancholia (9), and another group with bipolar depression (8), tended to under-estimate time to about the same extent. A group with manic or hypomanic disorders (11) tended to over-estimate. Patients with major depression without melancholia (9), bipolar disorders in remission (9), and dysthymic disorders (10), had no decided tendencies to under- or over-estimate short time intervals. The estimation of longer intervals (5-10 min.) was not significantly altered in the patient groups. The results are discussed in the context of earlier investigations, which mainly have yielded no changes in ability to estimate time intervals despite a subjective feeling that time is passing slowly or quickly in affective disorders.
Prospective time estimates were obtained from human subjects for stimulus durations ranging from 2 to 23 sec. Presence and absence of a concurrent nontemporal task was manipulated within subjects in three experiments. In addition, location of the task within temporal reproduction trials and psychophysical method were varied between groups in Experiments 2 and 3, respectively. For long-duration stimuli, the results of all three experiments conformed to results in the literature, showing a decrease in perceived duration under concurrent task conditions, in accord with attentional resource allocation models of timing. The effects of task location and psychophysical method on time estimates were also compatible with this analysis. However, psychophysical functions obtained under task conditions were fit well by power functions, an outcome that would not be anticipated on the basis of attention theory. The slopes of the functions under no-task conditions were steeper than those under task conditions. The data support the perceptual hypothesis that different sources of sensory input mediate timing under task and no-task conditions.